/Engine/Source/Runtime/GeometryCore/Public/VectorUtil.h
Fast cotangent of angle between two vectors (do not have to be normalized unit vectors). cot = cos/sin, both of which can be computed from vector identities
cotangent of angle between V1 and V2, or zero if result would be unstable (eg infinity)
namespace UE { namespace Geometry { namespace VectorUtil { template<typename RealType> RealType UE::Geometry::VectorUtil::VectorCot ( const [TVector](API\Runtime\Core\Math\TVector)< RealType > & V1, const [TVector](API\Runtime\Core\Math\TVector)< RealType > & V2 ) } } }